1. Field of the Invention
The present invention relates to a system for minimizing the lubrication pumping requirements of an engine equipped with a camshaft-operated valve train.
2. Disclosure Information
Oiling systems for the valve machinery of conventional internal combustion engines have been the topic of numerous inventions attempting to deal with problems arising from the need to provide adequate lubrication for those portions of the valve train subjected to high contact pressure. Such areas include the valve stem tip to rocker arm interface, and particularly, the camshaft lobe to lifter interface. Conventionally, a large volume of oil has been circulated to the camshaft and its associated machinery. It is one object of the present invention to reduce this volume of oil without sacrificing adequate camshaft and lifter lubrication.
U.S. Pat. No. 1,684,955 to Goodwin, U.S. Pat. No. 4,644,912 to Umeha et al. and U.S. Pat. No. 4,949,683 to Swars all disclose systems in which oil is conducted through hollow camshafts. Although the system shown in the '955 patent allows timed introduction of the oil to the vicinity of the valve lifter, it suffers from the deficiency that its concentric camshaft arrangement would be expected to exhibit a high frictional drive requirement. As a result, the parasitic losses associated with such a system would be unacceptable.
Camshafts are typically provided with oil introduced through the cam journals in the manner shown in U.S. Pat. No. 4,392,463 to Yasuhara at FIG. 3. Thus, a bearing surrounding the camshaft journal is provided with a slot which feeds oil into the interior of the camshaft. Unfortunately, if nothing more is done to control the consumption of oil by the camshaft, the power requirement associated with operating the engine's oil pump so as to have a sufficient volume of oil available to the camshaft, may be excessive. It is an object of the present invention to provide an intermittent oiling system for a camshaft and its associated valve train which minimizes the amount of oil pumped through the camshaft, thereby minimizing the capacity of the engine's oil pump required to handle the camshaft's lubrication requirements.
U.S. Pat. No. 4,258,673 to Stoody, Jr. et al., U.S. Pat. No. 4,711,203 to Seidl and U.S. Pat. No. 4,974,561 to Murasaki et al. disclose systems in which oil is provided via a camshaft support having a port formed therein for squirting oil upon part of the engine's valve train, other than the camshaft.
U.S. Pat. No. 3,116,647 to Leake and U.S. Pat. No. 3,628,513 to Grosseau disclose rocker arm arrangements allowing timed squirting of oil based upon the rotational position of the rocker arm.
It is an object of the present invention, as noted above, to produce an engine having minimal oil pump requirements associated with the valve train of the engine.
It is an advantage of a system according to the present invention that, due to the fact that less oil will be conducted into the upper part of the engine, the drainback holes required to allow the oil to fall back down to the crankcase may be minimized.
It is another advantage of the present invention that because less oil will be required to be brought to the top of the engine with this invention, less oil/air aerosols will be formed, thereby reducing the separation requirements which otherwise would be imposed upon the engine's positive crankcase ventilation system. Mitigation of formation of oil/air aerosols is beneficial because movement of lubricating oil into the engine exhaust may have adverse effects upon the life of catalytic exhaust emission control devices.